Concentric line oscillator



Sept. 24, 1946. H] TURNER I 2,408,355

' CONCENTRIC LINE OSCILLATOR.

Filed Jan. 29, 1942 2 Sheets-Sheet 1 H407 f 'l'UN/IBLL' LIA/E Tu/MBLE v LIA/E Zmventor Gttorneg Alfred if. Turnerv r I F1 6 I e t; 24, 1946. A H, TURNER 2,408,355

CONCENTRIC LINE OSCILLATOR Filed Jan. 29, 1942 2 Sheets-Sheet 2 3nventor rfi II. 'lurner I Gttomeg Patented Sept. 24, 1946 2,408,355 C NG T Q L C LLATOR Alfred H..Turner, Collin Radio Corporation of Delaware gswood, N. J assignor to 1 America, a corporation Ap ca ion Jan ary 29, 1942, Ser a N91 438.456

(01. zsoe-ss) 5 Claims. 1

M n entio r l es o c m e. os i ato s for producing radio frequency energy having h t w le ths ch. as e en t s i he centimeter wave region.

It is sometimes desirable to employ triodes or he mu i-e en a uum u s rat r ha ma netrons r the ike or o u in r h frequency energy. Triodes and similar vacuum tubes a e b n ec a e ign d for hi r quency use, but for some applications it has been founddifiicult to make them oscillate at a high enough frequency.

One object of my invention i to provide an imoved os la or to o uc ng y high. fr uencyeue y- A further object Qfthfl invention is to provide an im ro d iode sc l ator fo producing gh fre en y ener Astill further object of the invention is to provide an improved oscillator of the -grounded grid type. v

In a preferred embodiment of the invention, there is employed a triode so designed as to reduce the electron transit time and the interelee-trode capacitiesto a minimum. The plateand cathode are connected to two tunable circuits or lines, respectively. comprising concentric conductors. The grid would be grounded if usualpractice were followed, but it has been found that Oscillations can be obtained at a higher frequency if the grid is connected through some capacity to ground. This capacity provides feedback coupling" which functions in' phase with the feedback through the plate-cathode tube capacity to maintain high frequency oscillations.

The invention will be betterunderstood from the following description, taken in connection with the accompanying drawings in which Fig. 1 is a circuit diagram of a preferred 'embodiment of the invention,

Fig. 2 is a side view, partly in section, of the oscillator shown schematically in Fig. 1 (the. view being drawn two times full scale),

Fig. 3 is an enlarged view taken on the section 33 oi'Fi g. 2, and

Fig.4 illustrates another embodiment ofthe invention.

In the several-figures, like parts are indicated by like reference characters.

In Big. 1 the oscillator comprises a triode H1 designed to have very small inter-electrode capacities C1, C2 and C3. The particular vacuum tube that is illustrated and described by way of exampleis the General Electric type ZP446. The valuesof the tube capacities C1, C2 and C given on the drawings are for a particular tube. The cathode, grid and plate are indicated by the reference characters ll, l2 and 13, respectively.

The oscillator circuit basically is of the well known grounded grid type, although, in accordance with the present invention, the grid I2 is connected through a capacitor I4 to ground. The capacity of element I4 depends upon the circult and particular tube employed, but usually will be somewhere between 14 mmf. and 100 mmf. A grid leak resistor 16 is connected across capacitor I l. The plate I3 is connected to one conductor of a line ll|8, which maybe tuh ed by means of a capacity changing element t9 to adjust the oscillator frequency The cathode II is connected to one conductor 'of a line 2 |'22 which may be tuned by means of a shorting bar 23.

Fig 2 shows a preferred construction of the oscillator Q f'I FlgJ 1. The cathode, grid and plate terminals of the tube ID are shown atll, 12, and I3, respectively. The grid terminal I2 is the edge of a washer-shapedpiece of metal supporting the grid and sealed to 'glassections indicated as such by the shading. The plate terminal plug l3 and the plate itself are supported on a metal disc I5 sealed to the upper glass section. The cathode terminal portion l I is a metal shell forming the tube -base. One cathode heater lead is shown at 25. The cathode and the other side ofthe cathode heater are connected through a plurality of parallel lead-s 27 to a metal disc 28.

The tunable line 2l22 comprises two concentric cylinders, the outer cylinder. 22 being fastened at the bottom by bolts 29 to the bottom plate 28 and. being fastened at the top in screw-threaded relation to a metal cap portion 3|. The inner cylinder 21 is supported at the bottom by an outturned edge soldered to outer disc 28. The upper edge of cylinder 2| is slotted to form fingers that make electrical contact with the cathode through the terminal I 1-.

The shorting bar 2.3 comprises a ring surrounding the cylinder 2] and having fingerthat make contact therewith and having other fingers that make contact with the outer cylinder 22. This ring or shorting bar 23 may beslid along the cylinders 2| and 22 by means of rods 320i insulating material extending through openingsin the bottom plate 28.

The tunable line l'l-l 8 alsocomprises two con,- centric metal cylinders. In the specificstructure shown, the cylinders .I1 and 18 are enclosed by a protective cylinder 33 which i supported at the bottom by means of a metal cup-shaped member 34 which it engages inscreW-threaded rela- 3 tion. The cup member 34 and the cap member 3i preferably are also welded or soldered together.

The cylinder 18 of the line l'l--l8 preferably is soldered or welded to the cup member 36 and is given further mechanical support by a surrounding ring 36 that is bolted to the bottom of member 34 by several bolts 31, only one of which is shown in the drawings.

The cylinder 11 is supported from the cylinder l8, by meanof studs 38 of insulating material, only one of which is shown, each stud 38 being fastened in screw-threaded relation to the cylinder IR. A spacing washer 39 .of insulating material is located between the two cylinders H and 18.

The lower end of cylinder I! is electrically connected to both the upper plug portion 13' and the supporting disc portion I5 of the anode terminal a contacting ring 66 and the capacity between the ring 66 and'the end of cylinder 62, the ring and cylinder being separated by a mica washer 61; and the cylinder 63 is coupled to the anode terminal l3 by coupling-capacity at the spacing provided by an insulating bushing 58. The anode and cathode circuits may be tuned by shorting bars indicated at- 59 and H, respectively.

From the foregoing, it will be apparent that I have provided a simple oscillator employing a comparatively small and inexpensive vacuum tube that, because of the presence of the capacity l4 between grid and ground, may be made to oscillate at a higher frequency than is possible if the plate-cathode capacity C1 alone is depended upon to provide the necessary feedback.

by means of contacting rings M and i2, respec tively, having contacting fingers thereon. Connection" is made from the anode terminal to a plate voltage source (not shown) through a conductor 43 and through a choke coil 44 and a conductor 46 supported in and insulated from a metal tube 41.

The line tuning containing a circular slot so that it is, in effect, a. cup that may be moved into the space between cylinders I! and E8 to change the capacity between them. The tuning cup I9 is supported on an insulated rod 48 which is supported in screwthreaded relation in a disc 49 fastened into the end of the cylinder l8.

As shown in Figs. 2 and 3, the capacity id between the tube grid and ground is provided between the inner periphery of the cap 3| and a metal ring or triangular shaped member 5|, the surfaces of, the two elements being spaced apart the proper amount by a mica washer 52. The grid terminal I2 is connected to the ring 5! through a, contacting ring 53 having contacting fingers thereon. The resistor I6 is connected between the ring 5| and the cap 3|.

The rin 5! is supported by the bolts 3'| which extend through the tab portions extending from the ring. Insulating bushings 54 prevent groundin of rin 5i; they also provide the proper spacing to hold the washer 52 and the contacting member 53 in place but, at the same time, permit member 53 to move laterally a slight amount when a tube is inserted whereby it will be aligned for better contact.

The specific oscillator illustrated in Fig. 2 is designed to oscillate at 3,000 megacycles (10 centimeters). The frequency is determined principally by the line l1-l8 as tuned by the cup [9 and to a less extent by the line 2l-22, the posi tion of the shorting bar 23 on the line 2l-22 not being very critical. Since the line 11-48 would be too short for convenient mechanical construction at such a high frequency if made a quarter wave length long, it is made threequarters of a wave length long in the example described.

element I9 is a metal block I claim as my invention:

1. An oscillator comprising a vacuum tube having a cathode, a control grid and an anode, a tuned circuit having one terminal connected to said anode and having the ather terminal connected through a capacity element to said grid,

and a second tuned circuit having one terminal connected to said cathode and having the other terminal connected through said capacity ele-v ment to said grid whereby regenerative feedback is provided both by the anode-cathode capacity of said tube and by said capacity element.

2. An oscillator comprising a vacuum tube hav-.

ing a cathode, a control grid and an anode, a tuned anode circuit having one terminal connected to said anode and having the other ter-.

minal connected through a capacity element to said grid, and a tuned cathode circuit having one terminal connected to said cathode and having the other terminal connected through said capacity element to said grid whereby said capacity ele-' ment is common to said anode and cathode In Fig. 4 there is shown an embodiment of the invention in which the outer cylindrical member 6! which forms part of the tuned cathode circuit surrounds the other cylindrical members 62 and 03 that form the tuned anode circuit. In this construction the cylinder 62 functions as one circuits to provide regenerative feedback which aids that provided by the anode-cathode capacity of said tube.

3. An oscillator comprising two pairs of con-' ductors which are isolated from each other by a partition of conducting material, a vacuum tube having anode, cathode and control grid terminals, said anode terminal being connected to one conductor of one of said pairs, said cathode being connected to one conductor of the other of said pairs, the other conductors of said pairs and said partition being conductively connected to each other, and means for capacitively coupling said grid terminal to said partition whereby there is provided additional regenerative feedback coupling to aid the coupling provided by the anodecathode capacity of the tube.

4. An oscillator comprising two pairs of concentric conductors which are positioned end-toend along a common axis, a centrally apertured portion of conducting material separating said two pairs and connected to one conductor of each of said pairs, a vacuum tube having anode and cathode terminals at opposite ends and having a control grid terminal positioned intermediate the other tube terminals, said anode terminal being connected to the other conductor of one of said pairs, said cathode being connected to the other conductor of the other of said pairs-and means for capacitively coupling said grid terminal to said partition whereby there is provided additional feedback coupling between said pairs of conductors.

of said tuned anode circuit, said cathode terminal being connected to the other terminal of said tuned cathode circuit, and means for capaeitively coupling said grid terminal to said partition whereby there is provided additional regenerative feedback coupling from said anode circuit to said Cathode circuit.

ALFRED H. TURNER. 

